<!DOCTYPE html>
<html>
<head>
<style>
#myDIV {
  border: 1px solid black;
}
</style>
</head>
<body>

<div id="myDIV">
  <h2 class="example">A heading with class="example" in div</h2>
  <p class="example">A paragraph with class="example" in div.</p> 
</div>

<p>Click the button to change the text of the first element with class="example" in div.</p>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
  var x = document.getElementById("myDIV");
  x.querySelector(".example").innerHTML = "Hello World!";
}
</script>

</body>
</html>
